1. Technical Field
The present invention relates to an electronic device where a first substrate and a second substrate are bonded to each other in a state of interposing a bonding resin having photosensitivity between the first substrate and the second substrate, and a method for manufacturing the same.
2. Related Art
An electronic device is a device including a drive element such as a piezoelectric element which is deformed by applying a voltage, and is applied to various types of apparatuses or sensors. For example, in a liquid ejecting apparatus, various types of liquids are ejected from a liquid ejecting head using the electronic device. As such a liquid ejecting apparatus, for example, there is an image recording apparatus such as an ink jet type printer or an ink jet type plotter, but recently, the liquid ejecting head using the electronic device is also applied to various types of manufacturing apparatuses by using a feature which enables to accurately land a very small amount of liquid at a predetermined position. For example, the liquid ejecting head using the electronic device is applied to a display manufacturing apparatus that manufactures a color filter of a liquid crystal display or the like, an electrode forming apparatus that forms an electrode of an organic electro luminescence (EL) display, a field emission display (FED) or the like, and a chip manufacturing apparatus that manufactures a biochip (biochemical element). A liquid ink is ejected from a recording head for the image recording apparatus, and solutions of each of color materials of red (R), green (G), and blue (B) are ejected from a color material ejecting head for the display manufacturing apparatus. Moreover, a liquid electrode material is ejected from an electrode material ejecting head for the electrode forming apparatus, and a solution of a bio-organic matter is ejected from a bio-organic matter ejecting head for the chip manufacturing apparatus.
The liquid ejecting heads described above include the electronic device where a pressure chamber forming substrate on which a pressure chamber communicating with a nozzle is formed, a piezoelectric element (one type of drive element) which causes a pressure change to be generated in the liquid of the pressure chamber, and a sealing plate (which may be referred to as a protective substrate) which is arranged by being spaced with a gap against the piezoelectric element are stacked. In recent years, a technology of arranging a drive circuit relating to a driving of an actuator such as the piezoelectric element in the sealing plate has been developed. Therefore, a technology of bonding the substrates to each other by an adhesive agent (adhesive resin) which is configured of a photosensitive resin in a state of being spaced with a space between the substrates has been proposed (for example, see JP-A-2000-289197). In addition, a structure in which the substrates are stacked by a bonding resin (hereinafter, photosensitive resin) having photosensitivity in order to respond to high wiring density or miniaturization thereof, is adopted in a semiconductor package of micro electro mechanical systems (MEMS) such as various types of sensors.
FIG. 8A to FIG. 8D are process drawings for describing examples of bonding processes of substrates in the related art. As illustrated in FIG. 8A, a photosensitive resin 53 is applied onto a first substrate 52, and thereafter, as illustrated in FIG. 8B, the applied photosensitive resin 53 is patterned into a predetermined shape through exposure and developing. However, if the photosensitive resin 53 is not cured to a certain degree at the time of the developing, there is concern that the photosensitive resin 53 is peeled off from the substrate or the shape collapses, or there is a problem that patterning accuracy is lowered. Regarding the photosensitive resin 53, although the curing also proceeds at the time of the exposure, it is preferable that the curing proceeds by 50% or more before the developing, after the photosensitive resin 53 is fixed onto the substrate in order to suppress a defect at the time of the developing. Therefore, a heat treatment (prebaking) is performed before the developing. On the other hand, since the curing of the photosensitive resin 53 proceeds by the heat treatment in this manner, in the state where the substrates are bonded to each other as illustrated in FIG. 8C and FIG. 8D, there are problems that an adhesive strength of the photosensitive resin 53 is insufficient, and adhesion reliability is lowered.